A file transfer protocol client is a software used to access a data server through FTP. It establishes a connection and sends FTP commands to the server. FTP is part of the upper application layer of the IP suite, and the client sets up communication modes. The client uses two TCP connections, the control connection, and the data connection. The data connection is temporary and unique in how it is established. Security is an integral part of the client’s operation due to the general lack of security in FTP.
A file transfer protocol client is a computer software application used to access a data server using file transfer protocol (FTP). Through the use of this common protocol, the client is able to transfer data to and from the server. The client application provides the means to establish a connection and then send the appropriate FTP commands to the server. It comes in many forms, operated through a command line interface (CLI), a graphical user interface (GUI), even a common web browser.
FTP is part of the upper application layer of the Internet Protocol (IP) suite, with Transmission Control Protocol (TCP) used to carry communications. The file transfer protocol client, then, is responsible for establishing the connection to the server by finally opening two TCP connections. The first is the control connection, where the client sends commands to the FTP server. The first commands sent over the control connection are the USER command, with the user name as an argument, then the PASS command followed by the password. Once established, the control connection remains open throughout the session.
Here, the file transfer protocol client sets up the different communication modes it will have with the server. Typically, data is represented in one of two ways, text or binary, depending on the data being sent or received. Text type transfers are most often used for plain text files encoded with the American Standard Code for Information Interchange (ASCII) encoding method. Binary mode, also known as image mode, is for transferring files in a non-text binary format, such as digital images. Another, called local mode, is another way FTP can transfer data using a unique or proprietary format.
The second TCP channel used by the File Transfer Protocol client is the data connection. This connection is temporary in nature and is created only when a client requests a list of files on the server or is transferring a file to or from the server. The data connection is then destroyed when no data transfer takes place. The data connection is also unique in the way it is established, both actively and passively. The client must tell the server which type of data connection to use depending on the type of connection available on the client.
With an active data connection, the file transfer protocol client tells the server which TCP port number to use for the data connection. When used in passive mode, however, the client simply tells the server that it is passive, and the server then tells the client which TCP port to use for the data connection. In most cases, the client is set up for a passive connection thanks to the use of firewalls that protect it from unauthorized access.
As a result of the general lack of security in FTP, security for a file transfer protocol client is an integral part of its operation so that user activity is safe from prying eyes. Over the years several additional security techniques have been devised for use with FTP, such as the client explicitly naming a security protocol to use or automatically implying one. Other clients attempt to use FTP through a Secure Shell (SSH) tunnel, which may struggle due to the fleeting nature of the data connection.
Protect your devices with Threat Protection by NordVPN
